Lee was an aggressive and audacious commander. He liked taking the battle to the enemy and he was good at it. At Gettysburg however he didn't have enough information to make a better decision. He also believed his troops were pretty much unstoppable. He didn't realize how decimated some of his regiments were. The artillery that was supposed to clean out the Union center went over their heads. He underestimated how many troops the north had or how well they were dug in. He took the fight to the enemy with everything he had and lost. That's all there was to it.